Industrial sewing machines put to practical use include an automatic sewing machine which automatically sews a fabric according to a predetermined stitching pattern by driving the fabric or the needle thereof in accordance with preprogrammed stitching information retained in a storage device. The stitching information is held on a storage medium in the storage device, which medium can be changed to ensure ease of sewing different stitching patterns. A semiconductor memory, a magnetic card or the like is generally employed as a storage medium, and contains control information on how the sewing machine will operate according to the sequence of stitching operations. The control information generally includes control commands such as relative displacement between the needle and the fabric, stitching velocity and other parameters per stitch of the stitching pattern. The control information for one stitching pattern is a set of such control commands per stitch.
To perform automatic sewing of a desired stitching pattern on an automatic sewing machine, therefore, it is necessary to create control data corresponding to that stitching pattern and store it on a predetermined storage medium.
FIG. 4 is a perspective side view of a prior art stitching data creating device for a sewing machine 1, as shown in the Japanese patent disclosure bulletin No. 1985-148582. In front of the device is a tablet digitizer 10 having a menu area 11 and a pattern entry area 13 for data entry. A cursor 12 is used to select required items from the menu area 11 and to obtain coordinate data from the pattern entry area 13. On the face of the device is an LED display panel 20, having various switches and LEDs, a CRT 26 for displaying pattern data and an integrated circuit (IC) socket 18. The socket is designed to receive an IC PROM cassette as a storage medium for receiving the stitching data for later read-out. An eraser 8 is used for bulk erasing of the stitching data written on the PROM.
FIG. 5 is a block diagram illustrating a hardware configuration of the device. A bus 15 forms a common communication path for the system and connects a CPU 14 to the tablet digitizer 10, via an interface 48, as well as to storage devices, including ROM 22 and RAM 24. The bus 15 also connects to a display subsystem at interface 32, the subsystem including a CRT display 26, DMA controller 30 and storage RAM 28. The bus 15 also interfaces to a combination PROM write device 16/LED display unit 20 which loads a PROM cassette useable for controlling the operation of a sewing machine 38 via controller 40.
Operation of the device shown in FIG. 4 will now be described. Various modes and operating procedures are identified on the menu area 11 and are selectable by the cursor 12 in order to specify the control parameters for a stitching operation. Once in the data input mode, the relevant modes and operating procedures for data input are displayed on the LED display panel 20 as I/0 data via the interface 44. By drawing a desired stitching pattern on the tablet digitizer 10 by means of a cursor 12, stitching pattern data is written as pattern data signals by the PROM write device 16 onto a PROM cassette 42 via an interface 44 under control of CPU 14. When the loaded PROM cassette 42 is installed in a sewing machine controller 40, the sewing machine 38 can be driven to sew a predetermined pattern.
The PROM cassette 42 is installed into a PROM cassette socket 18, as shown in FIG. 4. A program for writing input data from the tablet digitizer 10 into the PROM via an interface 48 and under control of the CPU 14 is stored in ROM 22, and the CPU 14 performs processing in accordance with that program. The input stitching pattern data from the tablet digitizer 10 is temporarily stored in a data memory RAM 24. This data is stored as relative value data which indicates the X-Y coordinate data of the tablet digitizer 10 in terms of X-Y variations of each stitch.
The CRT monitor 26 is provided to monitor the writing of data from the tablet digitizer 10 into the PROM 16. The stitching pattern data in the data memory RAM 24 is converted into picture displaying data by the CPU 14 and is stored in a picture data memory RAM 28 via an interface 32 on bus 15. When digital values in RAM 28 are converted into analog values (voltages) by D/A converters 34 and 36, a stitch pattern figure is displayed on the CRT 26 by a CRT control circuit 46. This enables an operator to enter data while simultaneously checking that data as a picture.
A specific entry operation will now be described in accordance with FIG. 6 which shows an example of a stitch pattern. First, a home position P1 of the pattern on the tablet digitizer 10 is specified by means of the cursor 12. In practice, this point will correspond to a mechanical origin of the XY table of the industrial sewing machine, not illustrated.
Then, by selecting a key for creating non-stitching feed data on the tablet digitizer 10 and specifying a point P2, non-stitching data is created along a straight line P1 P2. Then, a key for creating stitching data is selected and points P3, P4, . . . , P9 and P10 are specified to create stitch data. After selecting the non-stitching data creation key again at point P10, point P11 is specified, thereby creating non-stitching data along P10 P11. Further, after entering stitching points P12, P13, . . . , and P19 in a similar manner, appropriate keys are selected for creating trimming data and end data to complete creation of the stitch data.
In the above entry operation, thread trimming data is automatically created at any point of switching from stitch data to non-stitching data, e.g., at the point of switching from the straight line P9 P10 to P10 P11.
FIG. 7 is a flow chart indicating the above operation for creating sewing data. Initially, a switch on the cursor 12 is checked for the ON state (step S1). If ON, an XY coordinate value of the point P1 is read (S2) and stored in the data memory RAM 24 (S3), and that value is further converted into stitch data of the sewing machine and stored in the data memory RAM 24 (S4). Thereafter points P2, P3, P4, . . . , and P19 are operated upon in a similar manner.
FIG. 8 illustrates an example of the content of the data memory RAM 24 storing the stitch pattern data shown in FIG. 6. Referring to FIG. 8, (x.sub.1, y.sub.1), (x.sub.2, y.sub.2), (x.sub.3, y.sub.3), . . . , and (x.sub.19, y.sub.19) indicate areas storing data read from the tablet digitizer 10. Similarly, (x.sub.1a, y.sub.1a), (x.sub.s, y.sub.s), (x.sub.2a, y.sub.2a), . . . , (x.sub.17a, y.sub.17a), (x.sub.18a, y.sub.18a), (x.sub.t, y.sub.t), and (x.sub.e, y.sub.e) indicate data as converted into stitching data for the sewing machine. (x.sub.1, y.sub.1), . . . , and (x.sub.19, y.sub.19) are absolute value data read from the tablet digitizer 10, and (x.sub.1a, y.sub.1a), . . . , and (x.sub.18a, y.sub.18a) are relative value data calculated by the following expression: EQU x.sub.na =x.sub.n+1 -x.sub.n EQU y.sub.na =y.sub.n+1 -y.sub.n
where, n=1, 2, 3, . . . , 17, 18
The converted stitch data includes data sets (x.sub.s, y.sub.s) and (x.sub.t, y.sub.t) and that of (x.sub.e, y.sub.e). Data (x.sub.s, y.sub.s) is a two-byte start datum added when non-stitching data is switched to the stitch data, data (x.sub.t, y.sub.t) is thread trimming data for trimming the thread used in stitching, and data (x.sub.e, y.sub.e) is a two-byte end datum added to the end of the input data.
When operated according to this stitch pattern data, the electronic sewing machine stitches from P1 to P2 to P3 . . . P18 to P19, then returns from P19 to P1, to start the next stitching run. If the retraced distance from P19 to P1 is long in this case, a lot of time will be lost in the stitching work, resulting in inefficiency. To improve working efficiency, a first stitching operation from P1 to P2 to P3 . . . P18 to P19 is performed and sewing is temporarily stopped here. Then the object to be sewn is changed and a second stitching operation from P19 to P18 to P17 . . . P2 to P1 is performed.
An example of a data entry for enabling such reverse sewing of the stitch pattern shown in FIG. 6 will now be described in reference to FIG. 9. Initially, P1 to P2 to P3 . . . P18 to P19 are entered in a manner illustrated in FIG. 6. Data for temporarily stopping the electronic sewing machine (a halt code) is entered at P19. Then P20 to P21 to P22 . . . P35 to P36 to P37 are entered in correspondence with P18 to P17 to P16 . . . P3 to P2 to P1 by tracing the pattern backwards. At the final point, P37, end data indicating the end of the stitch pattern data is entered.
FIG. 10 shows an example of the contents of the data memory RAM 24 when the entire stitch pattern in FIG. 9 has been entered point by point by the operator. The contents of the RAM 24 include data for each of points P1-P37, converted into the stitch data of the sewing machine. A data set (x.sub.p, y.sub.p) in FIG. 10 indicates the halt code for temporarily stopping the electronic sewing machine at point P19.
When manually entering the stitch pattern data shown in FIG. 9, for example, data in strict correspondence with the previously input points P18, P17 . . . and P1 must be entered as the points P20, P21, . . . P37. However, it is extremely difficult to do this because of the large number of input points P18, P17, . . . and P1 and the inaccuracy of manual operation (the cursor is generally operated by hand).
An attempt to make a straightforward substitution of the data for points P1-P19 to create data for points P19-P37 would result in errors. FIG. 11 shows data obtained by replacing the (x.sub.e, y.sub.e) datum of the stitch data in FIG. 7 with the halt datum (x.sub.p, y.sub.p) and simply reversing the order of the remaining data. Comparison between FIG. 11 and the correct reverse stitch data in FIG. 10 indicates that the thread trimming datum (x.sub.t, y.sub.t) and the start datum (x.sub.s, y.sub.s) are generated at incorrect positions.
Accordingly, it is an object of the present invention to reduce operator input for reverse stitching data.
It is a further object of the present invention to automatically generate reverse stitching data from forward input stitching data in a reverse stitching data generation operation.
It is yet another object of the present invention to overcome the disadvantages in the prior art by providing reverse stitching data, automatically generated on the basis of one-way stitching data.